The present invention relates to vacuum brake-boosters of the tandem type, used especially for assisting the braking of motor vehicles.
Such brake-boosters have been known for a long time, and documents DE-A-3,505,626, FR-A-2,431,623 and U.S. Pat. No. 4,516,474, to mention only a few, describe various models of these.
These tandem brake-boosters are of relatively complicated construction, which results in high production costs. In particular, the two movable pistons which are separated by a stationary plate both have to be fixed to a movable hub.